Automatic air bleed valves are used during operations to remove air from installations in which a fluid flows, and to allow encapsulated air to escape during operation of such an installation. Commercial air bleed valves, as are in use for example in heating installations, are generally set up to operate under operational pressures up to a maximum of 7 bars, and therefore, are unsuitable for use in hydraulic installations where higher pressures generally prevail.
Most of these air bleed systems work with floats which are moved by the operating medium and which, through a mechanism, operate a valve to release the encapsulated air into the environment. Thus, power or force is obtained for operational use through the float arrangement or through the float specific weight- An air bleed system in a hydraulic system, as a result of the low density of the operating media, clearly has less setting or adjusting forces easily available for operation of the opening mechanism. This leads to disturbances in operation. Particularly, failing to accomplish complete closing of the conventional air bleed valve with a setting in a hydraulic range leads to undesired escape into the environment of air with operating medium carried in it, comparable to an aerosol. Such leads to endangerment of the health of the operators entrusted with monitoring such hydraulic installations.
With a different class of air bleed valve, as disclosed in German Utility Patent 77 38 268, the float raises the valve plate completely from the outlet opening by means of the lever system. A progressively greater linear passageway aligned in a plane is required of the valve plate, until complete closing is attained. This requires an air bleed valve of very large structure. In addition to the undesired aerosol discharge, the closing process does not proceed in a controlled manner. Thus, fluid discharge from the outlet opening into the environment is possible. Upon opening, it can even lead to inadvertent escapements, which make the opening process difficult or even entirely impossible.
In an air bleed valve of the same class, as in German Publication 22 41 645, the lever system is formed of a valve rod arranged in the valve plate, horizontally when it is in the closed position. A spherical float moves the disk-shaped flat valve plate by pivoting for opening and closing a conical outlet opening. Because of the high operational forces required for the lever system, that float is constructed as a large member. The float, in combination with the transverse lever rods, leads to an air bleed valve of large construction. The valve plate is formed of a flat sheet which can be moved away from the outlet opening dependent upon the pressure forces only with difficulty. This can lead to escapements from the area of the lever system and to negative effects on the operation of the air bleed valve.